Based on their results, the researchers recommended further research into treatment regimens that do not contain nucleoside reverse transcriptase inhibitors (NRTIs) – such as Truvada – which currently form the backbone of antiretroviral therapy. They also noted that longer trials with more participants would be needed to confirm the long-term safety and efficacy of non-NRTI-based regimens.

The results were presented last week at the 6th International AIDS Society Conference on HIV Pathogenesis, Treatment, and Prevention (IAS 2011).

Traditional combination antiretroviral therapy regimens consist of two NRTIs plus at least one additional anti-HIV drug from a different class. However, due to side effects associated with NRTIs and the fact that some patients cannot take them due to allergies or other conditions, researchers have begun exploring alternative “NRTI-sparing” regimens (see related AIDS Beacon news).

In this study, researchers examined the efficacy of the non-NRTI-based regimen of Kaletra (lopinavir/ritonavir) plus Selzentry (maraviroc) versus the more traditional regimen of Kaletra plus Truvada (emtricitabine/tenofovir). Truvada is a combination of two NRTIs, while Kaletra is a protease inhibitor and Selzentry is a CCR5 inhibitor, which is a relatively new type of antiretroviral.

The trial included 38 HIV-positive adults who had not previously been treated for HIV. Half the participants were randomly assigned to receive Kaletra plus Selzentry, and the other half were assigned to take Kaletra plus Truvada. The researchers then assessed participants’ CD4 (white blood cell) counts and viral loads (amount of HIV in the blood) at 4, 12, 24, 36, and 48 weeks after starting treatment.

Results showed that after 48 weeks, participants in the non-NRTI Kaletra plus Selzentry group had significantly higher increases in CD4 counts than participants in the Kaletra plus Truvada group. The average increase in CD4 count for the Kaletra/Selzentry group was 226 cells per microliter, compared to 125 cells per microliter in the Kaletra/Truvada group.

Additionally, most participants in the non-NRTI group (83 percent) achieved undetectable viral loads by week 12, compared to less than half of patients in the Truvada group. By 48 weeks, 95 percent of participants in the Kaletra/Selzentry group had undetectable viral loads, compared to 83 percent of participants in the Kaletra/Truvada group.

The researchers also noted that three participants taking Kaletra plus Truvada had to interrupt treatment due to diarrhea. Overall one person in the Kaletra/Truvada group discontinued treatment, compared to none in the Kaletra/Selzentry group.

For more information, please see the study abstract and presentation (pdf) on the IAS 2011 conference website.